DE-OS 20 00 326 discloses a dust collector for a Banbury mixer in which the shafts of mixing rotors of a mixing device are sealed at their ends by sealing arrangements. In the sealing arrangement, the opening for the shaft is sealed by an annular end plate rigidly secured to the mixer housing and by a packing ring which is compressed against a shaft connector by means of a pressure spring. A sealing contact which is effective over the entire shaft is obtained by controlling the sealing pressure.